/*
 * Copyright (c) 2003, 2004 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef HAVE_CONFIG_H
#include <config.h>
#endif

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif

#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#else
#include <sys/ioctl.h>
#endif

#include <sys/queue.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef WIN32
#include <syslog.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <event.h>
#include <evutil.h>
#include <log.h>

int evtag_decode_int (ev_uint32_t *pnumber, struct evbuffer *evbuf);
int evtag_encode_tag (struct evbuffer *evbuf, ev_uint32_t tag);
int evtag_decode_tag (ev_uint32_t *ptag, struct evbuffer *evbuf);

static struct evbuffer *_buf;	/* not thread safe */

void
evtag_init (void)
{
  if (_buf != NULL)
    return;

  if ( (_buf = evbuffer_new() ) == NULL)
    event_err (1, "%s: malloc", __func__);
}

/*
 * We encode integer's by nibbles; the first nibble contains the number
 * of significant nibbles - 1;  this allows us to encode up to 64-bit
 * integers.  This function is byte-order independent.
 */

void
encode_int (struct evbuffer *evbuf, ev_uint32_t number)
{
  int off = 1, nibbles = 0;
  ev_uint8_t data[5];

  memset (data, 0, sizeof (data) );

  while (number)
    {
      if (off & 0x1)
        data[off/2] = (data[off/2] & 0xf0) | (number & 0x0f);
      else
        data[off/2] = (data[off/2] & 0x0f) |
                      ( (number & 0x0f) << 4);

      number >>= 4;

      off++;
    }

  if (off > 2)
    nibbles = off - 2;

  /* Off - 1 is the number of encoded nibbles */
  data[0] = (data[0] & 0x0f) | ( (nibbles & 0x0f) << 4);

  evbuffer_add (evbuf, data, (off + 1) / 2);
}

/*
 * Support variable length encoding of tags; we use the high bit in each
 * octet as a continuation signal.
 */

int
evtag_encode_tag (struct evbuffer *evbuf, ev_uint32_t tag)
{
  int bytes = 0;
  ev_uint8_t data[5];

  memset (data, 0, sizeof (data) );

  do
    {
      ev_uint8_t lower = tag & 0x7f;
      tag >>= 7;

      if (tag)
        lower |= 0x80;

      data[bytes++] = lower;
    }

  while (tag);

  if (evbuf != NULL)
    evbuffer_add (evbuf, data, bytes);

  return (bytes);
}

static int
decode_tag_internal (ev_uint32_t *ptag, struct evbuffer *evbuf, int dodrain)
{
  ev_uint32_t number = 0;
  ev_uint8_t *data = EVBUFFER_DATA (evbuf);
  int len = EVBUFFER_LENGTH (evbuf);
  int count = 0, shift = 0, done = 0;

  while (count++ < len)
    {
      ev_uint8_t lower = *data++;
      number |= (lower & 0x7f) << shift;
      shift += 7;

      if (! (lower & 0x80) )
        {
          done = 1;
          break;
        }
    }

  if (!done)
    return (-1);

  if (dodrain)
    evbuffer_drain (evbuf, count);

  if (ptag != NULL)
    *ptag = number;

  return (count);
}

int
evtag_decode_tag (ev_uint32_t *ptag, struct evbuffer *evbuf)
{
  return (decode_tag_internal (ptag, evbuf, 1 /* dodrain */) );
}

/*
 * Marshal a data type, the general format is as follows:
 *
 * tag number: one byte; length: var bytes; payload: var bytes
 */

void
evtag_marshal (struct evbuffer *evbuf, ev_uint32_t tag,
               const void *data, ev_uint32_t len)
{
  evtag_encode_tag (evbuf, tag);
  encode_int (evbuf, len);
  evbuffer_add (evbuf, (void *) data, len);
}

/* Marshaling for integers */
void
evtag_marshal_int (struct evbuffer *evbuf, ev_uint32_t tag, ev_uint32_t integer)
{
  evbuffer_drain (_buf, EVBUFFER_LENGTH (_buf) );
  encode_int (_buf, integer);

  evtag_encode_tag (evbuf, tag);
  encode_int (evbuf, EVBUFFER_LENGTH (_buf) );
  evbuffer_add_buffer (evbuf, _buf);
}

void
evtag_marshal_string (struct evbuffer *buf, ev_uint32_t tag, const char *string)
{
  evtag_marshal (buf, tag, string, strlen (string) );
}

void
evtag_marshal_timeval (struct evbuffer *evbuf, ev_uint32_t tag, struct timeval *tv)
{
  evbuffer_drain (_buf, EVBUFFER_LENGTH (_buf) );

  encode_int (_buf, tv->tv_sec);
  encode_int (_buf, tv->tv_usec);

  evtag_marshal (evbuf, tag, EVBUFFER_DATA (_buf),
                 EVBUFFER_LENGTH (_buf) );
}

static int
decode_int_internal (ev_uint32_t *pnumber, struct evbuffer *evbuf, int dodrain)
{
  ev_uint32_t number = 0;
  ev_uint8_t *data = EVBUFFER_DATA (evbuf);
  int len = EVBUFFER_LENGTH (evbuf);
  int nibbles = 0;

  if (!len)
    return (-1);

  nibbles = ( (data[0] & 0xf0) >> 4) + 1;

  if (nibbles > 8 || (nibbles >> 1) + 1 > len)
    return (-1);

  len = (nibbles >> 1) + 1;

  while (nibbles > 0)
    {
      number <<= 4;

      if (nibbles & 0x1)
        number |= data[nibbles >> 1] & 0x0f;
      else
        number |= (data[nibbles >> 1] & 0xf0) >> 4;

      nibbles--;
    }

  if (dodrain)
    evbuffer_drain (evbuf, len);

  *pnumber = number;

  return (len);
}

int
evtag_decode_int (ev_uint32_t *pnumber, struct evbuffer *evbuf)
{
  return (decode_int_internal (pnumber, evbuf, 1) == -1 ? -1 : 0);
}

int
evtag_peek (struct evbuffer *evbuf, ev_uint32_t *ptag)
{
  return (decode_tag_internal (ptag, evbuf, 0 /* dodrain */) );
}

int
evtag_peek_length (struct evbuffer *evbuf, ev_uint32_t *plength)
{

  struct evbuffer tmp;
  int res, len;

  len = decode_tag_internal (NULL, evbuf, 0 /* dodrain */);

  if (len == -1)
    return (-1);

  tmp = *evbuf;

  tmp.buffer += len;

  tmp.off -= len;

  res = decode_int_internal (plength, &tmp, 0);

  if (res == -1)
    return (-1);

  *plength += res + len;

  return (0);
}

int
evtag_payload_length (struct evbuffer *evbuf, ev_uint32_t *plength)
{

  struct evbuffer tmp;
  int res, len;

  len = decode_tag_internal (NULL, evbuf, 0 /* dodrain */);

  if (len == -1)
    return (-1);

  tmp = *evbuf;

  tmp.buffer += len;

  tmp.off -= len;

  res = decode_int_internal (plength, &tmp, 0);

  if (res == -1)
    return (-1);

  return (0);
}

int
evtag_consume (struct evbuffer *evbuf)
{
  ev_uint32_t len;

  if (decode_tag_internal (NULL, evbuf, 1 /* dodrain */) == -1)
    return (-1);

  if (evtag_decode_int (&len, evbuf) == -1)
    return (-1);

  evbuffer_drain (evbuf, len);

  return (0);
}

/* Reads the data type from an event buffer */

int
evtag_unmarshal (struct evbuffer *src, ev_uint32_t *ptag, struct evbuffer *dst)
{
  ev_uint32_t len;
  ev_uint32_t integer;

  if (decode_tag_internal (ptag, src, 1 /* dodrain */) == -1)
    return (-1);

  if (evtag_decode_int (&integer, src) == -1)
    return (-1);

  len = integer;

  if (EVBUFFER_LENGTH (src) < len)
    return (-1);

  if (evbuffer_add (dst, EVBUFFER_DATA (src), len) == -1)
    return (-1);

  evbuffer_drain (src, len);

  return (len);
}

/* Marshaling for integers */

int
evtag_unmarshal_int (struct evbuffer *evbuf, ev_uint32_t need_tag,
                     ev_uint32_t *pinteger)
{
  ev_uint32_t tag;
  ev_uint32_t len;
  ev_uint32_t integer;

  if (decode_tag_internal (&tag, evbuf, 1 /* dodrain */) == -1)
    return (-1);

  if (need_tag != tag)
    return (-1);

  if (evtag_decode_int (&integer, evbuf) == -1)
    return (-1);

  len = integer;

  if (EVBUFFER_LENGTH (evbuf) < len)
    return (-1);

  evbuffer_drain (_buf, EVBUFFER_LENGTH (_buf) );

  if (evbuffer_add (_buf, EVBUFFER_DATA (evbuf), len) == -1)
    return (-1);

  evbuffer_drain (evbuf, len);

  return (evtag_decode_int (pinteger, _buf) );
}

/* Unmarshal a fixed length tag */

int
evtag_unmarshal_fixed (struct evbuffer *src, ev_uint32_t need_tag, void *data,
                       size_t len)
{
  ev_uint32_t tag;

  /* Initialize this event buffer so that we can read into it */
  evbuffer_drain (_buf, EVBUFFER_LENGTH (_buf) );

  /* Now unmarshal a tag and check that it matches the tag we want */

  if (evtag_unmarshal (src, &tag, _buf) == -1 || tag != need_tag)
    return (-1);

  if (EVBUFFER_LENGTH (_buf) != len)
    return (-1);

  memcpy (data, EVBUFFER_DATA (_buf), len);

  return (0);
}

int
evtag_unmarshal_string (struct evbuffer *evbuf, ev_uint32_t need_tag,
                        char **pstring)
{
  ev_uint32_t tag;

  evbuffer_drain (_buf, EVBUFFER_LENGTH (_buf) );

  if (evtag_unmarshal (evbuf, &tag, _buf) == -1 || tag != need_tag)
    return (-1);

  *pstring = calloc (EVBUFFER_LENGTH (_buf) + 1, 1);

  if (*pstring == NULL)
    event_err (1, "%s: calloc", __func__);

  evbuffer_remove (_buf, *pstring, EVBUFFER_LENGTH (_buf) );

  return (0);
}

int
evtag_unmarshal_timeval (struct evbuffer *evbuf, ev_uint32_t need_tag,
                         struct timeval *ptv)
{
  ev_uint32_t tag;
  ev_uint32_t integer;

  evbuffer_drain (_buf, EVBUFFER_LENGTH (_buf) );

  if (evtag_unmarshal (evbuf, &tag, _buf) == -1 || tag != need_tag)
    return (-1);

  if (evtag_decode_int (&integer, _buf) == -1)
    return (-1);

  ptv->tv_sec = integer;

  if (evtag_decode_int (&integer, _buf) == -1)
    return (-1);

  ptv->tv_usec = integer;

  return (0);
}
